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Technology: Wire Structure Of Cable Products And The Way Of Stranding
Nov 13, 2017

  The structure of the conductor is not only the variety and material of the material, but also the size and composition of the cross section.Most of the wire and cable products structure of round wire, because in the long strip products circular cross section is the most stable structure, when equal cross section perimeter shortest (can save material) geometry;So the circular wire is the basic structure of cable products.Some of these other shapes are required, and this article will also be introduced.

The basic structure of the wire - the circle

  1. The main varieties of single round line are copper single wire, aluminum single wire and copper aluminum alloy wire, with wire diameter as structural parameters, ranging from 0.01mm to 3.00 mm.A single strand of a single strand is used for product use, most of which is a semi-finished product which is twisted into a multi-strand strand.

In addition to single - material circular single line, there are compound round single line.Commonly used with double metal circular single wire, such as the aluminum clad steel wire (aluminum conductivity is high, the steel wire tensile resistance strong), copper clad aluminum wire (high conductivity copper, aluminum light) and single wire coating, such as tin plated copper wire, nickel plated copper wire.

  2, round wire cable is a product of great length and subjected to many times in the production, installation and use of winding and open, large cross-section wire if not use the small diameter of single stranded made a certain section of stranded wire, the product will not be able to manufacture and use.Different conditions and conditions require different softness of wire and cable - bending or twisting performance.Therefore, there are different requirements for the winch of various kinds of products in terms of softness and so on, so in the standard of the conductors, seven wire structures are specified, and table 1 is the standard specified wire structure.

Material the same cross section equal wire can use several structures, namely single root number and the diameter is different, in the same cross section when the more the number of single wire (the more single wire diameter), the higher the softness of the wire.

The structural parameters of the circular strand are the cross-sectional area (mm2), single line root and single line diameter (mm), and joint diameter ratio.

  3. The derivative structure of the circular strand

In the process of wire stranding, the winch shall be pressed tightly by the tightening wheel and so on, so that the conductor can account for 90% of the cross section.One is to compress the protruding shape of the wire surface, which is beneficial to the thin (0.5-1mm) of the high-voltage crosslinking polyethylene cable, which is not easily punctured in the inner semiconductor layer (uniform electric field).The second is to reduce the space between the single lines.

(2) is equipped with empty slots in the round in the stranded wire slot for 14 to 18 mm in diameter, and there are two kinds of products, namely the oil-filled cable as oil tank of oil flow, large current cable as a general in the gas or liquid cooling channel (can increase the current-carrying).The conductor of oil filling cable usually adopts the Z line or the bow-shaped single strand to make the circular section, or the round single wire is twisted into a spiral tube.The inner grooves used as internal cooling forced cooling are sealed with metal pipes.

(3) the fan wire is in the low voltage 3-4 core oiled paper insulated power cable, and the conductor structure (1-10 kv), is to make paper insulation insulation wire core after the shape of a 3 120 °, ground into a round shape when cabling (4 core cable for three 100 °, neutral line 60 ° fan), to a large number of outer material saving.Lines are rarely used.

Other shaped wire structures

  1. Flat wire and sheet material will be made into a long strip of flat shape that is many times larger than the thickness.The flat line is mainly used for enameled wire and wrap line to meet the needs of medium size, large scale and even special large motor and transformer insertion line.In addition to the use of the switchboard, the main power plant, substation and large manufacturing workshop supply the large current of the bus (also known as the busbar).A large (several thousand square mm) busbar can be made into a groove.The busbar is a naked conductor, and it must be installed with an insulator to insulate it.

The structural parameters of flat wire and plate are sectional area, width, thickness and radians of four corners.

 2, the structure of the coaxial cable wires as the information transmission using coaxial cable with "a" work for a loop, which wires are single circle, and outside conductor must be surrounded by a cylindrical of concentric circles on the outside, inside and outside the conductor to maintain concentric circles must rely on the support, so the structure of the outer conductor is closely related to the support structure.If use a hard outer conductor copper tape is applied to longitudinally wrap round tube, and longitudinal rolling into thread for bending, the support can adopt embedded chip insulation support, such as supporting the use of solid core or like lotus root in the hole or foam insulation, the outer conductor can use copper wire package, such as braided structure.Usually, the coaxial cable is embedded in a small coaxial or micro-coaxial cable that is generally used to weave or wrap the outer conductor structure of the copper wire.

  3, namely USES the specific shape of the conductor cross section conductor, is as a general as a conductor in motor, switch components, such as motor commutation equipment material, the knife switch in the components of the cutting tools, etc.In addition to the thick round copper rod as the conductor, there are also products of gourd type and gutter type.

  4. Non-metallic conductors such as optical fiber in fiber optic cables, conductive plastic wire used for automobile point of ignition and audio cable, etc.

The twist of the round winch

The circular strand of various sections of a circular single strand of the same diameter is usually used in the following three types of wrings: regular heave, irregular heave (band) and composite heave (compound).Some special product lines are also used in different diameters and other structures.

  1. There are several characteristics of the regular twisted round winch: the single line diameter is the same;The center layer is 1 single line, the first layer is 6, and each layer increases by 6.;The direction of each strand is opposite, but the outermost layer must be the right (Z direction). The aim is to connect the two segments of the wire.Therefore, the structure of the regular stranded conductor is the most stable, which is good for bending, twisting, winding and outer diameter of the smallest and round shape, and the single line will not be loose when the strand is cut off.So are widely used in electric power system with wire and cable, namely the Ⅰ, Ⅱ kind of conductor structure in table 1.

  2, ground beam For softness excellent electric wire electric cable wires must adopt Ⅲ - Ⅴ class conductor structure in table 1.The characteristic is: the number of wire root is the most (up to 200), single line diameter wire (the smallest is about 0.05 mm), and it must be twisted and twisted.

Beam or stranded stranded (bundle) method is to dozens of thin single stratification through a small circle beam together, and then in the same direction lay (similar to the cotton yarn twisting after doubling), through the lines forming.Bundle of stranded wire diameter is not very strict, appearance also can only approximate circle, but as a result of single wire between relatively loose, single thin, so is more soft, in crowded or package the insulation can basically control product is circular in shape.

  3. The complex winging is necessary to require the product to be very soft and the conductor section is larger. The conductor section of the wire shall be 2562/0.3 if the conductor section is 185mm2 of mine cable.

Double - twist is to put dozens of single strands into a strand line, and then twisted into a wire by means of a regular strand.Sometimes, it is also used to double - wring, about 7-19 strands strand to become "big", and then "big" as single stranded.


Cross section of the reeled conductor

Technical parameters of the winch

   In the process of winding, several important technological parameters must be controlled, which is actually the technical parameter of the strand structure, which must be specified in the product design and executed by the process document.Main technical parameters: pitch ratio, heave, heave.

   1, section diameter than the stranded wire is a single line to outer spiral direction went up to the outside of the inner surface (see figure 2), such as the one strand, can see the single spiral Angle alpha (called haul in Angle).A single line along the inner layer of wire around a week length L;PI D 'in the figure shows the circle length of the center line of the single line of the layer, D 'is the center diameter of the circle;H is the distance along the center line in the direction of the single line of the hinged joint, which is called the joint pitch.


(a)Twisted conductor shape   (b)Single line expansion

Normal twisted single line expansion drawing

  The ratio of the strand to the diameter of the strand divided by the diameter of the strand is called "the diameter ratio m", which is the main technological parameter in the wire heave, which is comparable.

In theory, the diameter of the calculation pitch ratio should be based on the diameter of the center line of the single line of this layer.But for practical convenience, the measured outer diameter of the layer is calculated (called the practical diameter ratio).The calculation formula of the utility pitch ratio is as follows: (h, D unit is mm)

The diameter ratio is larger, namely, the Angle of the Angle is larger, which reflects the small degree of strangulation, and vice versa.The diameter of the section is smaller than the wire, the strand is tight, the structure is stable, the wire is soft, the bending is good, but the production speed is slow.Therefore, in the product standard, there is a specified range for the twisted diameter ratio of the conductor.

  2. The ratio of the winging rate to a pitch length of the strand is the ratio of the length of the single line to the pitch of the strand, which is called the heave coefficient, and the percentage rate is called the winging rate.

The rate of wring is mainly used for the calculation of production organization and material consumption.

  3. In the filling coefficient wire, the ratio of the single cross section to the area of the section of the wire is called the filling coefficient eta, and the value is always less than 1.(1- eta) represents the void fraction in the cross section.The center is a regular stranded conductor with an eta of about 0.75.

Some products such as crosslinked polyethylene power cable, waterproof sealing cable wire.The eta can be increased to 0.89-0.92 by using a deeply pressed wire.The filling coefficient large conductor, when water vapor and other through insulation, because single line air hole forming capillary state, can prevent water vapor to extend to the sides, prevent the extension of external damage.After the wire compacted, the single line especially the outermost single line deformation is more serious, but the surface of the wire is more rounded.The tension wire is slightly harder when compared with the unpressed pressure.

  4. There are only two kinds of twisted directions in the heave of single strand, i.e. the left hand direction (s direction) and the right direction (z direction).There are two adjacent layers in the normal stranding structure which must be twisted in different direction.The first layer is the left direction, then the second layer is to the right, and the purpose of the interchange is to stabilize the structure, and it will not break out when the wire is disconnected.